Display system and method

ABSTRACT

The present disclosure relates to a display system ( 1 ) for generating a composite view of a region behind a vehicle (V) towing a trailer (T). A first camera (C 1 ) is provided for outputting first image data corresponding to a first image (IMG 1 ), the first camera (C 1 ) being configured to be mounted in a rear-facing orientation to the vehicle (V). A second camera (C 2 ) is provided for outputting second image data corresponding to a second image (IMG 2 ), the second camera (C 2 ) being configured to be mounted in a rear-facing orientation to the trailer (T). An image processor ( 5 ) receives the first image data and said second image data. The image processor ( 5 ) is configured to combine said first image data and said second image data to generate composite image data corresponding to a composite image (IMG 3 ). The present disclosure also relates to a corresponding method of generating a composite image (IMG 3 ), and to a rig made up of a vehicle (V) and a trailer (T).

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/504,821, filed Feb. 17, 2017, which itself is a 35 U.S.C. § 371national stage application of PCT Application No. PCT/EP2015/068970,filed on Aug. 18, 2015, which is a Continuation-In-Part of PCTApplication No. PCT/EP2015/068080, filed on Aug. 5, 2015, which claimspriority from Great Britain Patent Application No. 1414632.8 filed onAug. 18, 2014, the contents of which are incorporated herein byreference in their entireties. The above-referenced PCT InternationalApplication was published in the English language as InternationalPublication No. WO 2016/026870 A1 on Feb. 25, 2016.

TECHNICAL FIELD

The present disclosure relates to a display system for a vehicle towinga trailer, to a method of generating a composite image, and to a rigcomprising a vehicle and a trailer.

BACKGROUND

It is common practice to tow a trailer behind a vehicle. A particularproblem encountered while towing is the reduced visibility behind thevehicle. In particular, the trailer presents an obstacle which partiallysecures the driver's field of view behind the vehicle. Large and smalltrailers typically reduce visibility and create a blind spot behind thevehicle. The resulting lack of visibility can, for example, compromisethe following manoeuvres: lane changes, overtaking, parking, joining amotorway (highway) and pulling out of junctions.

In order to mitigate the aforementioned problems, it is common practiceto fit a so-called towing mirror to the side mirrors of the vehicle. Thetowing mirrors extend laterally outwardly to provide improved visibilityalong the side of the trailer. However, towing mirrors have severaldisadvantages, notably they increase the vehicle width and may reducemanoeuvrability in confined spaces. Moreover, towing mirrors are notwell suited to providing a view of other vehicles positioned directlybehind the trailer. Towing mirrors can also suffer from vibration andhence blurring of the image.

It is known to provide a rear-facing camera on a vehicle to enable arear-view image to be displayed in the vehicle cabin, for example on anelectronic display. However, when a trailer is being towed behind thevehicle, the image generated by the rear-facing camera will be at leastpartially obscured. As a consequence the image may include blind spots,for example in lateral regions alongside the trailer.

It is against this backdrop that the present invention has beenconceived. At least in certain embodiments, the present invention seeksto overcome or ameliorate at least some of the aforementioned problemsassociated with prior art devices.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to display system for a vehicletowing a trailer, to a method of generating a composite image, to a rigcomprising a vehicle and a trailer.

According to a further aspect of the present invention there is provideda display system for a vehicle, the display system comprising:

-   -   a first camera configured to be mounted in a rear-facing        orientation to the vehicle and to output first image data;    -   a second camera configured to be mounted in a rear-facing        orientation to a trailer towed by the vehicle and to output        second image data; and    -   processor means for receiving said first image data and said        second image data and for generating a composite image        therefrom.

According to another aspect of the invention for which protection issought there is provided a processor or control module for a vehicle,the processor or control module being configured and/or arranged toreceive first image data from a first camera disposed in a rear-facingorientation relative to the vehicle and second image data from a secondcamera disposed in a rear-facing orientation relative to a trailer towedby the vehicle, and to generate a composite image from said first andsecond image data.

The processor or control module may be configured to output thecomposite image to a display system, such as a screen or digital displayof the vehicle.

The display system may comprise a rear-view display system. Theresulting composite image may be a rear-facing composite image which, atleast in certain embodiments, can facilitate towing the trailer. In use,the first camera may be mounted to the vehicle and at least a portion ofthe first image may comprise a view of the front of the trailer. Thesecond camera can be mounted to the rear of the trailer such that thesecond image is unobstructed. However, the second image does not providethe driver with an indication of the relative position and/ororientation of the trailer. As such, the driver of the vehicle may findit difficult to judge the relative position of obstructions and/or othervehicles to the trailer using the second image. By combining the firstimage data and the second image data, the view of the front of thetrailer from the first image can be composited with the unobstructedsecond view. The first image can, for example, be displayed as atransparent or semi-transparent layer which overlays the second image(for example to provide a phantom or ghost image of the trailer). Thecomposite image data can be output to a display screen to display thecomposite image.

The image processor can be configured to combine said first image dataand said second image data such that at least a portion of one of saidfirst image and said second image is overlaid onto the other of saidfirst image and said second image. At least said portion of one of saidfirst image and said second image can be overlaid as a transparent orsemi-transparent image onto the other of said first image and saidsecond image. In one implementation, the image processor can beconfigured to overlay at least a portion of said first image onto saidsecond image to form the composite image data.

The image processor can be configured to select the portion of saidfirst image or of said second image to be overlaid in dependence on animage mask. The image mask can be predefined or can be generated independence on the first image data. The first image data can be analysedto identify the trailer in the first image. The image mask cancorrespond to the trailer identified in the first image. The analysis ofthe first image can, for example, comprise performing edge detection orfeature identification.

The image processor can be configured to combine said first image dataand said second image data such that a portion of said first image or ofsaid second image is substituted with at least a portion of the other ofsaid first image and said second image.

The image processor can be configured to analyse said first image dataand said second image data to identify one or more features common toboth said first image and said second image. The image processor can beconfigured to match (align) said first image and said second image independence on the identified one or more features. The image processorcan be configured to perform one or more of the following transforms tosaid first image and/or said second image:

image rotation, scaling, cropping, magnification, skew correction andtranslation. These transforms could, for example, compensate fordifferent viewing angles and/or imaging properties of the first andsecond cameras.

The image processor can be configured to generate said composite imagein dependence on positional data defining the relative position of thefirst and second cameras. The positional data can comprise longitudinalpositional data and/or vertical positional data and/or lateralpositional data. A longitudinal offset between the first and secondcameras can be used to facilitate registration of the first and secondimages. Alternatively, or in addition, the image processor cancompensate for a lateral offset and/or a vertical offset between saidfirst and second cameras.

The first camera can comprise a first wireless transmitter fortransmitting the first image data to the image processor and/or thesecond camera can comprise a second wireless transmitter fortransmitting the second image data to the image processor.Alternatively, a wired connection can be established between the imageprocessor and the first camera and/or the second camera.

The image processor can be configured to augment the composite imagewith one or more of the following:

-   -   a graphical representation of the trailer being towed by the        vehicle;    -   a graphical representation of a projected path for the trailer        during a reversing operation;    -   a vehicle control instruction(s) to guide the trailer during a        reversing operation; and    -   proximity information for the trailer.

The image processor can be a digital image processor. Alternatively, theimage processor can be an analogue image processor configured togenerate the composite image data.

The image processor can be configured to output the composite image datafor display on a display screen. The display screen could, for example,be disposed in a centre console, an instrument cluster, or a rear-viewmirror of the vehicle. Alternatively, the image processor can beconfigured to output the composite image data wirelessly, for example tobe displayed on a network device, such as a cellular telephone or aso-called “smart-phone”, a personal computer or a tablet computer.

According to a further aspect of the present invention there is provideda rig comprising a vehicle and a trailer, wherein the rig comprises adisplay system as described herein. The first camera can be mounted tothe vehicle and the second camera can be mounted to the trailer.

According to a further aspect of the present invention there is provideda display system for providing a view of a region behind a vehicle, thedisplay system comprising:

-   -   a camera for mounting in a rear-facing orientation to a trailer,        the camera being operable to output image data corresponding to        an image;    -   an image processor for receiving said image data;    -   wherein the image processor is configured to overlay a graphical        representation of the trailer onto the image data to form an        augmented image for display.

According to a further aspect of the present invention there is provideda method of generating a composite image of a region behind a vehicletowing a trailer, the method comprising:

-   -   using a first camera disposed on the vehicle to generate a first        image;    -   using a second camera disposed on the trailer to generate a        second image;    -   using an image processor to combine said first and second images        to form a composite image.

The method can comprise overlaying at least a portion of one of saidfirst image and said second image onto the other of said first image andsaid second image. The image to be overlaid onto the other image can bemodified to be rendered in a transparent or semi-transparent form. Atleast said portion of one of said first image and said second image canbe overlaid as a semi-transparent image onto the other of said firstimage and said second image. An image mask can be used to select theportion of said first image or of said second image to be overlaid. Theimage mask can be generated in dependence on the first image data.

The process of combining said first and second images can comprisesubstituting a portion of said first image or of said second image withat least a portion of the other of said first image and said secondimage.

The method can comprise identifying one or more features common to bothsaid first image and said second image. The method can comprise matchingsaid first image and said second image in dependence on the identifiedone or more features. The method can comprise performing imageregistration to match (align) the first and second images with eachother. The image registration can be performed substantially inreal-time by the image processor.

The method can comprise performing one or more of the followingtransforms to said first image and/or to said second image: imagerotation, scaling, cropping, magnification, skew correction andtranslation.

The composite image can be generated in dependence on positional datadefining the relative position of the first and second cameras.

The method can comprise augmenting the composite image with one or moreof the following:

-   -   a graphical representation of the trailer being towed by the        vehicle;    -   a graphical representation of a projected path for the trailer        during a reversing operation;    -   a vehicle control instruction(s) to guide the trailer during a        reversing operation; and    -   proximity information for the trailer.

The method can comprise displaying the composite image, for example on adisplay screen. The display screen can be provided in a centre consoleor an instrument cluster. Alternatively, or in addition, the displayscreen can be incorporated into a rear view mirror.

According to a further aspect of the present invention there is provideda display system for generating a composite view of a region behind avehicle towing a trailer, the display system comprising:

-   -   a first camera for outputting first image data corresponding to        a first image, the first camera being configured to be mounted        in a rear-facing orientation to the vehicle;    -   a second camera for outputting second image data corresponding        to a second image, the second camera being configured to be        mounted in a rear-facing orientation to the trailer;    -   a first lateral camera for outputting first lateral image data        corresponding to a first lateral image;    -   a second lateral camera for outputting second lateral image data        corresponding to a second lateral image;    -   an image processor for receiving said first image data, said        second image data, said first lateral image data and said second        lateral image data;    -   wherein the image processor is configured to combine said first        image data, said second image data, said first lateral image        data and said second lateral image data to generate composite        image data corresponding to a composite image. By incorporating        the first and second lateral images into the composite image,        the display system can provide a more comprehensive        representation of the area around a vehicle and a trailer being        towed by the vehicle. The first lateral image can comprise a        first side of the trailer; and the second lateral image can        comprise a second side of the trailer.

The image processor can be configured to combine said first image data,said second image data, said first lateral image data and said secondlateral image data such that at least a portion of said first image isoverlaid onto one or more of said second image, said first lateral imageand said second lateral image. The at least a portion of said firstimage can, for example, be overlaid as a semi-transparent image onto oneor more of said second image, said first lateral image and said secondlateral image.

The image processor can be configured to form an intermediate compositeimage by combining one or more of the following: the second image, thefirst lateral image and the second lateral image. The first lateralimage can be disposed on a first side of the second image. The secondlateral image can be disposed on a second side of the second image. Theimage processor can perform one or more transform to match the secondimage to the first and second lateral images. The one or more transformcan, for example, comprise translation, scaling, cropping and rotation.The image processor can be configured to overlay said at least a portionof the first image onto the intermediate composite image.

The image processor can be configured to identify one or more featurecommon to both said first image and said intermediate composite image.The image processor can be configured to match said first image and saidintermediate composite image in dependence on the identified one or morefeature.

The first lateral image and/or the second lateral image can have avertical height substantially equal to a vertical height of the secondimage. The lateral image data can extend the full height of thecomposite image.

Alternatively, the first lateral image can have a vertical height whichis less than a vertical height of the second image; and/or the secondlateral image can have a vertical height which is less than a verticalheight of the second image. The first and second lateral image data canhave a smaller vertical extent. The region(s) above the first lateralimage and/or the second lateral image data can be infilled with thesecond image data to create the composite image.

The first lateral image and/or the second lateral image can be insertedinto the second image data to form said intermediate composite image.The images can be joined along boundaries, for example by stitching theimages together.

The first lateral camera can be a first side-mounted camera. The secondlateral camera can be a second side-mounted camera. The firstside-mounted camera can be mounted to a first side of the vehicle. Thesecond side-mounted camera can be mounted to a second side of thevehicle. In certain embodiments, the first side-mounted camera can bemounted to a first side of the trailer. The second side-mounted cameracan be mounted to a second side of the trailer.

The image processor can be configured to perform one or more of thefollowing transforms: image rotation, scaling, cropping, magnification,skew correction and translation. The one or more transform can beapplied to one or more of the: first image, second image, first lateralimage, and second lateral image.

The image processor can be configured to output the composite image datafor display on a display screen.

According to a further aspect of the present invention there is provideda rig comprising a vehicle and a trailer, wherein the rig comprises adisplay system as claimed in any one of the preceding claims; whereinthe first camera, the first lateral camera and the second lateral cameraare mounted to the vehicle; and the second camera is mounted to thetrailer.

According to a still further aspect of the present invention there isprovided a method of generating a composite image of a region behind avehicle towing a trailer, the method comprising:

-   -   using a first camera to generate a first image;    -   using a second camera to generate a second image;    -   using a first lateral camera to generate a first lateral image;    -   using a second lateral camera to generate a second lateral        image;    -   using an image processor to combine said first image, said        second image, said first lateral image and said second lateral        image to form a composite image.

The method can comprise overlaying at least a portion of the first imageonto one or more of said second image, said first lateral image and saidsecond lateral image. The at least a portion of the first image can beoverlaid as a semi-transparent image.

The method can comprise forming an intermediate composite image bycombining one or more of the following: the second image, the firstlateral image and the second lateral image. The at least a portion ofthe first image can be overlaid onto the intermediate composite image.

The method can comprise identifying one or more feature common to bothsaid first image and said intermediate composite image. The first imageand the intermediate composite image can be matched in dependence on theidentified one or more feature.

The first lateral image and/or the second lateral image can have avertical height substantially equal to a vertical height of the secondimage in said intermediate composite image.

Alternatively, the first lateral image can have a vertical height lessthan a vertical height of the second image; and/or the second lateralimage can have a vertical height less than a vertical height of thesecond image. The method can comprise inserting the first lateral imageand/or the second lateral image into the second image to form saidintermediate composite image.

The method can comprise displaying the composite image data on a displayscreen.

The term processor is used herein to refer to one or more electronicprocessors. Similarly, the term system memory is used herein to refer toone or more storage devices. The processor can be a general purposecomputational device configured to execute a set of softwareinstructions to perform the method(s) described herein.

Within the scope of this application it is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. That is, all embodimentsand/or features of any embodiment can be combined in any way and/orcombination, unless such features are incompatible. The applicantreserves the right to change any originally filed claim or file any newclaim accordingly, including the right to amend any originally filedclaim to depend from and/or incorporate any feature of any other claimalthough not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described,by way of example only, with reference to the accompanying figures, inwhich:

FIG. 1 shows a vehicle and a trailer incorporating a rear-view displaysystem in accordance with an embodiment of the present invention;

FIG. 2 shows a schematic representation of the components of therear-view display system shown in FIG. 1;

FIG. 3A shows a first image from a first camera disposed on the vehicle;

FIG. 3B shows a second image from a second camera disposed on thetrailer;

FIG. 3C shows a composite image generated by combining the first andsecond images shown in FIGS. 3A and 3B;

FIG. 4 shows an augmented composite image generated by the rear-viewdisplay system shown in FIG. 1;

FIG. 5 shows a vehicle and a trailer incorporating an alternatearrangement of the rear-view display system;

FIG. 6 illustrates the formation of a composite image incorporatingimage data from the cameras in the alternate arrangement shown in FIG.5;

FIG. 7 illustrates an alternate formation of a composite imageincorporating image data from the cameras in the alternate arrangementshown in FIG. 5;

FIG. 8 illustrates the formation of a composite image incorporatingimage data from the cameras in the alternate arrangement shown in FIG.5; and

FIG. 9 illustrates the composition of the composite image using theformation shown in FIG. 8.

DETAILED DESCRIPTION

A rear-view display system 1 in accordance with an embodiment of thepresent invention will now be described with reference to theaccompanying figures. The rear-view display system 1 is intended for usein a vehicle V towing a trailer T (referred to in combination as a rig)to generate a composite image for providing improved visibility for thevehicle driver of the region behind the vehicle V. The vehicle V in thepresent embodiment is an automobile or a utility vehicle. However, itwill be appreciated that the rear-view display system 1 may beincorporated into other types of vehicle, such as a tractor unit.

The vehicle V has a first longitudinal axis X₁, and the trailer T has asecond longitudinal axis X₂, as shown in FIG. 1. The terms “front” and“rear” are used herein in their conventional sense when defining therelative position of features on the vehicle V and the trailer T. Theterms “rear-facing” and “rear-view” are used herein to refer to aposition or orientation which is in a direction towards the back of thevehicle V or the trailer T.

As shown in FIG. 1, the rear-view display system 1 is in the form of avehicle-mounted unit and a trailer-mounted unit. The vehicle-mountedunit comprises a central processing unit 3 connected to a first cameraC1. As shown in FIG. 2, the central processing unit 3 comprises an imageprocessor 5 coupled to system memory 7, and a wireless receiver 9 havinga first antenna 11. The image processor 5 can be a digital imageprocessor. The image processor 5 is configured to execute a set ofsoftware instructions held in the system memory 7. The image processor 5is connected to a communication bus 13, such as the vehicle CAN bus, forcommunicating with other vehicle systems. The vehicle V comprises adisplay screen 15 on which the images received from the first and secondcameras C1, C2 can be selectively displayed. The trailer-mounted unitcomprises a second camera C2 connected to a wireless transmitter 17having a second antenna 19.

The first and second cameras C1, C2 are both rear-facing digital camerasfor generating video images. The first and second cameras C1, C2 eachcomprise a wide-angle lens to provide a viewing angle of approximately130°. The first camera C1 is mounted centrally at the rear of thevehicle V above a rear license plate (not shown) and, in the presentembodiment, can selectively function as a reversing camera to provide aparking aid when there is no trailer T coupled to the vehicle V. Thesecond camera C2 is mounted centrally at the rear of the trailer T. Thefirst camera C1 has a first field of view FOV1 (shown in FIG. 1) havinga line of sight (i.e. a centreline) substantially coincident with thefirst longitudinal axis X₁. The second camera C2 has a second field ofview FOV2 (shown in FIG. 1) having a line of sight (i.e. a centreline)substantially coincident with the second longitudinal axis X₂, forexample above a license plate on the trailer T. The first and secondcameras C1, C2 are arranged at approximately the same vertical heightabove ground level. In alternate arrangements, the first and secondcameras C1, C2 can be offset from each other in a vertical and/ortransverse direction. The image processor 5 can be configured to correctfor any such positional offset. Equally, the image processor 5 can beconfigured to correct for an angular offset between the first and secondcameras C1, C2, for example if one or both of the first and secondcameras C1, C2 is angularly offset from the respective first and secondlongitudinal axes X₁, X₂.

The first camera C1 outputs a first signal S1 comprising first imagedata corresponding to a first image IMG1. The first signal S1 ispublished to the communication bus 13 and provides a first input for theimage processor 5. The second camera C2 outputs a second signal S2comprising the second image data corresponding to a second image IMG2.The second signal S2 is transmitted by the wireless transmitter 17 tothe wireless receiver 9 to provide a second input for the imageprocessor 5. The wireless transmitter 17 can transmit the second signalS2 using a suitable wireless communication standard, such as Wi-Fi®.

As outlined above, the first camera C1 is rear-facing and, when thevehicle V is towing the trailer T, the first image IMG1 contains thetrailer T which partially obstructs the view afforded to the driver in arearwards direction. The second camera C2 is mounted to the trailer Tand the second image IMG2 provides an unobstructed view of the scenebehind the trailer T. The image processor 5 is configured to combine thefirst image data and the second image data to generate composite imagedata. The composite image data corresponds to a composite image IMG3formed from said first and second images IMG1, IMG2.

The image processor 5 modifies the first image data such that the firstimage IMG1 will be rendered as a semi-transparent image. For example,the image processor 5 can modify an alpha channel or an indextransparency of the first image data. The first image data can bemodified to provide a transparency of 25%, for example. The first imagedata and the second image data are combined to form a composite imageIMG3. The image processor 5 can be configured to perform otherimage-manipulation techniques, for example to modify the colour and/orcontrast of one or more image, for example to highlight an outline ofthe trailer T. The image processor 5 may also be configured to implementan edge-recognition algorithm to identify an outline of the trailer Tfor display in the composite image IMG3. The resulting composite imageIMG3 comprises the second image IMG2 as a background element over whichthe first image IMG1 is overlaid. Significantly, the trailer T (which ispresent in the first image IMG1, but not the second image IMG2) ispartially visible in the composite image IMG3 to facilitate determiningits relative position to objects and/or other vehicles. The imageprocessor 5 can perform additional blending or smoothing functions toobscure the transition between the first and second images IMG1, IMG2 inthe composite image IMG3. The rear-view display system 1 may beconfigured to allow the user to select the modification to the firstimage data, for example to adjust a transparency setting of the firstimage data, to allow customisation of the composite image IMG3.

When the vehicle V and the trailer T are aligned with each other (suchthat the first and second longitudinal axes X₁, X₂ are coincident), thefirst and second images IMG1, IMG2 are in respect of the same scenealbeit offset from each other due to the longitudinal offset between thefirst and second cameras C1, C2. Moreover, there may be a lateral offsetand/or a vertical offset due to the positioning of the first and secondcameras C1, C2 on the vehicle V and the trailer T. Accordingly, thefirst image IMG1 cannot be overlaid directly onto the second image IMG2.Rather, the image processor 5 is configured to implement an imagematching procedure to align the first image IMG1 with the second imageIMG2. The image processor 5 can implement a cross-correlation techniqueautomatically to match features common to both the first image IMG1 andthe second image IMG2. The image processor 5 can, for example, use aHough transform feature extraction technique. The relative positionand/or orientation of the identified features can be compared in thefirst and second images IMG1, IMG2. Alternatively, or in addition, theimage processor 5 can identify the centroid of one or more imagefeatures and compare their relative position in the first and secondimages IMG1, IMG2. Other image analysis techniques that may be includedare point mapping and/or edge-recognition. The image processor 5 canoptionally perform image processing techniques with respect to time inorder to track movement of the identified features in the first andsecond images. The image processor 5 may retrieve vehicle dynamic datapublished to the communication bus 13 to refine analysis of the imagedata. For example, the image processor 5 may optionally utilise thevehicle speed and/or turning angle during analysis of the image data.The image processor 5 may also be configured to determine the relativeorientation of the trailer T by analysing a target 21 provided on thefront of the trailer T. In the illustrated arrangement, the target 21comprises three circles arranged in a triangular formation. The relativeorientation of the trailer T can be characterised as a hitch angle θdefining the angular orientation of the centrelines of the vehicle V andthe trailer T in a horizontal plane. The image processor 5 may also beconfigured to compensate for differences in the first and second imagesIMG1, IMG2 due to different specifications of the first and secondcameras C1, C2.

The image processor 5 utilises the results of the cross-correlation toperform image registration such that the first and second images IMG1,IMG2 are aligned with each other. The image registration can compriseone or more of the following transforms: image rotation, scaling,cropping, magnification (zooming), skew correction and translation. Itwill be appreciated that the transform(s) required to match the firstand second images IMG1, IMG2 depend on the relative positioning of thefirst and second cameras C1, C2. The transform(s) may be applied in twodimensions (2D) or three dimensions (3D), for example to compensate foran angular offset between the first and second longitudinal axes X₁, X₂(in a horizontal plane and/or a vertical plane). As outlined above, thefirst image IMG1 data is modified such that the first image IMG1 appearssemi-transparent when displayed. The first image IMG1 is then overlaidonto the second image IMG2 to form the composite image IMG3 (for exampleusing alpha-compositing techniques). The image processor 5 canoptionally edit the first image IMG1 such that only a portion thereof isoverlaid onto the second image IMG2. A cropping function may be appliedto a predefined region of the first image IMG1, for example having apredefined width and height. Alternatively, the image processor 5 may beconfigured to identify the trailer T within the first image IMG1 togenerate a mask which is overlaid onto the second image IMG2.

The operation of the rear-view display system 1 in accordance with anembodiment of the present invention will now be described with referenceto FIGS. 3A, 3B and 3C. The first camera C1 generates first image datacorresponding to a first image IMG1 which includes the trailer T beingtowed behind the vehicle V, as shown in FIG. 3A. The second camera C2generates second image data corresponding to a second image IMG2 whichis an unobstructed view of the region behind the trailer T, as shown inFIG. 3B. The image processor 5 implements an image matching procedure tomatch (align) the first and second images IMG1, IMG2, as describedherein. The image processor 5 modifies the first image data such thatthe first image IMG1 will be displayed as a partially transparent image.The first image data and the second image data is then combined to formcomposite image data. The composite image data corresponds to acomposite image IMG3 comprising the first image IMG1 overlaid onto thesecond image IMG2, as shown in FIG. 3C. The trailer T appears as a‘ghost’ image or grind of the composite image IMG3. The resultingcomposite image IMG3 provides a clear view of the region behind thetrailer T whilst retaining sufficient details of the trailer T to enablethe driver to determine its relative position to obstacles and othervehicles.

The composite image IMG3 is output for display on a display screen, suchas a liquid-crystal display, provided in the vehicle. The display screencan, for example, be provided in a centre console or in an instrumentcluster. Alternatively, or in addition, the display screen can beincorporated into a rear view mirror, for example to display thecomposite image IMG3 alongside a reflective image.

If the angular offset between the first and second longitudinal axes X₁,X₂ becomes excessive, for example during a turning manoeuvre, the imageprocessor 5 may be unable to match the first and second images. Theimage processor 5 may be configured to activate one or more side-mountedcameras (on the vehicle V and/or the trailer T) to obtain differentimages for processing. If this function is not available, the imageprocessor 5 can output a notification to the vehicle driver that therear-view display function is not available.

The rear-view display system 1 described herein can be modified todisplay additional information. By way of example, the composite imageIMG3 can be augmented by displaying a projected path P which the trailerT will follow during a reversing procedure. The projected path P can beoverlaid onto the composite image IMG3 when the vehicle V is placed inreverse and the trailer T is detected. The driver can use the projectedpath P to control the trailer T when the vehicle V is being reversed. Anillustration of an augmented composite image IMG4 is shown in FIG. 4 byway of example. Moreover, the rear-view display system 1 may be modifiedto display driver instructions, for example to provide vehicle controlinstructions (steering angle and/or transmission selection) for guidingthe trailer T to an identified parking area. Further details of avehicle control system for controlling a vehicle to facilitate parking atrailer are known from the applicant's earlier UK patent applicationGB1312036.5 filed on Jul. 4, 2013), the contents of which areincorporated herein in their entirety by reference.

In the illustrated example, the vehicle V is an automobile (for examplea sports utility vehicle) and the trailer T is a caravan. It will beappreciated, however, that the apparatus and method(s) described hereinare not limited in this respect and may be implemented in other typesand categories of vehicle and to other types of trailer. The apparatusand method(s) could, for example, be applied to an articulated vehicle,a semi-trailer or a tractor-trailer.

It will be appreciated that further changes and modifications can bemade to the apparatus and method described herein without parting fromthe scope of the present invention. A rear-view display system 1 hasbeen described herein with reference to a single first camera C1disposed on the vehicle V and a single second camera C2 disposed on thetrailer T. It will be appreciated that more than one rear-facing cameramay be provided on the vehicle V and/or the trailer T. By providing morethan one camera, the composite image IMG3 may provide a greater sense ofdepth perception.

The rear-view display system 1 can be configured to overlay the firstimage IMG1 onto the second image IMG2 when the vehicle V is travellingin a forwards direction such that the composite image IMG3 is displayedto enable the driver to identify other vehicles behind the trailer T.Alternatively, the rear-view display system 1 may be configured tooverlay the first image IMG1 onto the second image IMG2 only when thevehicle is parked or during a parking operation, for example when thetransmission of the vehicle V is placed in reverse.

Furthermore, rather than overlaying the first image onto the secondimage, a graphical representation of the trailer (for example asilhouette or an outline of the trailer T, or a graphical indicia) maybe overlaid onto the second image. Alternatively, a mask of the trailerT may be generated based on a static image generated by the first cameraC1 and overlaid onto the second image generated by the second camera C2.

The rear-view display system 1 has been described with reference to afirst camera C1 mounted to the rear of the vehicle V. In an alternatearrangement, the rear-view display system 1 can comprise a firstside-mounted camera mounted to a first side of the vehicle and/or asecond side-mounted camera mounted to a second side of the vehicle V.The first and second side-mounted cameras would be rearward-facing, forexample mounted to the side (wing) mirrors. The first side-mountedcamera and/or the second side-mounted camera may be used in conjunctionwith the vehicle-mounted first camera C1 and/or the trailer-mountedsecond camera C2. In particular, the image processor 5 can be arrangedto combine the first image IMG1 and/or the second image IMG2 with animage generated by the first side-mounted camera and/or the secondside-mounted camera. The image processor 5 may utilise the image(s) fromthe first side-mounted camera and/or the second side-mounted camera toprovide a partially transparent overlay on the first image IMG1 and/orthe second image IMG2. In this arrangement, the partially transparentoverlay can comprise a side view of the vehicle V, for example a view ofa rear quarter of the vehicle V. It will be appreciated that thisarrangement may be used when the vehicle V is not towing a trailer T, sothe second camera C2 may be omitted. The resulting composite image IMG3may be used during parking or reversing manoeuvres to provide asubstantially uninterrupted view of the area behind the vehicle V. Bydisplaying the image from the first side-mounted camera and/or thesecond side-mounted camera as a partially transparent overlay, thedriver can be provided with an indication of the extent of the vehicle Vto facilitate judgement of distances and/or position. The compositeimage IMG3 may be output to a display provided, for example, in thecentre console, the instrument cluster, the rear view mirror or a sidemirror display.

The alternate arrangement of the rear-view display system 1 isillustrated in FIG. 5; and the formation of a composite image from theimage data generated by the cameras is shown in FIG. 6. The rear-viewdisplay system 1 comprises a first side-mounted camera C3 mounted to afirst side of the vehicle V; and a second side-mounted camera C4 mountedto a second side of the vehicle V. The first and second side-mountedcameras C3, C4 are mounted to the side (wing) mirrors and haverespective third and fourth fields of vision FOV₃, FOV₄. As shown inFIG. 5, the third and fourth fields of vision FOV₃, FOV₄ extend alongthe respective sides of the vehicle V. This arrangement is advantageoussince it can provide coverage of the lateral regions of the trailer T.This is particularly relevant since the front of the trailer T mayobscure portions of the images generated by the first camera C1.Similarly, the images generated by the second camera C2 do not providecoverage along the sides of the trailer T. Consequently, there may beregions along the sides of the trailer T, particularly towards the rear,which are not covered by either of the first and second cameras C1, C2.The composite image IMG3 may therefore include blind spots. Furthermore,the presence of these blind spots may not be immediately apparent whenviewing the composite image IMG3 since the trailer T is displayed as asemi-transparent ‘ghost’ image which may give the impression of anuninterrupted view. The first and second side-mounted cameras C3, C4generate first and second lateral images IMG1L, IMG2L which can provideimproved coverage on each side of the trailer T. As illustrated in FIG.5, the third and fourth fields of vision FOV₃, FOV₄ can extend alongeach side of the trailer T at least when the vehicle V is travelling ina straight line.

As illustrated in FIG. 6, a second composite image IMG5 is formedcomprising the first and second lateral images IMG1L, IMG2L and thefirst and second images IMG1, IMG2. The components of the secondcomposite image IMG5 are illustrated in FIG. 6. The first and secondlateral images IMG1L, IMG2L are combined with the second image IMG2, forexample by stitching the first and second lateral images IMG1L, IMG2Land the second image IMG2. The image processor 5 can be configured tojoin the first and second lateral images IMG1L, IMG2L and the secondimage IMG2 at predefined boundaries or at dynamically determinedboundaries, for example determined in dependence on identification ofone or more common feature in the images. In the present embodiment, thefirst and second lateral images IMG1L, IMG2L are stitched to the leftand right hand sides respectively of the second image IMG2 alongvertical boundaries. As illustrated in FIG. 6, the first and secondlateral images IMG1L, IMG2L extend vertically for the full height of thesecond composite image IMG5. The first image IMG1 is then overlaid ontoan intermediate composite image formed by combining the second imageIMG2 and the first and second lateral images IMG1L, IMG2L. As in theprevious embodiment, the first image IMG1 is overlaid as asemi-transparent image onto the intermediate composite image. Inparticular, the image processor 5 modifies the first image data suchthat the first image IMG1 is displayed as a partially transparent imagewhich overlies a portion of each of the second image IMG2 and the firstand second lateral images IMG1L, IMG2L. In a variant, the first imageIMG1 may be overlaid onto the second image IMG2 which is then combinedwith the first and second lateral images IMG1L, IMG2L.

In a variant of the arrangement described above with reference to FIGS.5 and 6, the first and second side-mounted cameras C3, C4 each comprisea wide-angle lens, for example a fish-eye lens, and are arranged togenerate respective first and second lateral images IMG1L, IMG2Lextending along the sides of the vehicle V and the trailer T. The firstand second side-mounted cameras C3, C4 can have a view angle of 200° ormore. The first and second side-mounted cameras C3, C4 are arranged suchthat their respective focal centrelines are directed downwardly. Thefirst and second side-mounted cameras C3, C4 are mounted to the side(wing) mirrors and have respective third and fourth fields of visionFOV₃, FOV₄. The third and fourth fields of vision FOV₃, FOV₄ extendalong the respective sides of the vehicle V. The resulting first andsecond lateral images IMG1L, IMG2L encompass a region extending from thefront to the rear of the vehicle V. The resulting first and secondlateral images IMG1L, IMG2L can be used by other vehicle systems, forexample to assist with vehicle parking and/or to identify other vehiclesat a road junction. Due to the arrangement of the first and secondside-mounted cameras C3, C4, the first and second lateral images IMG1L,IMG2L typically only comprise a low-level region alongside the trailerT, for example a region below a horizontal plane in which the first andsecond side-mounted cameras C3, C4 are disposed. A third composite imageIMG6 is formed taking account of this limitation of the vertical extentof the first and second lateral images IMG1L, IMG2L.

The third composite image IMG6 comprises the first and second lateralimages IMG1L, IMG2L and the first and second images IMG1, IMG2. Thecomponents of the third composite image IMG6 are illustrated in FIG. 7.The first and second lateral images IMG1L, IMG2L are combined with thesecond image IMG2 to form an intermediate composite image. Thecombination can, for example, comprise stitching the first and secondlateral images IMG1L, IMG2L and the second image IMG2. The region in thethird composite image IMG6 vertically above the first and second lateralimages IMG1L, IMG2L is formed from the second image IMG2. The firstimage IMG1 is then overlaid onto the intermediate composite image formedby combining the second image IMG2 and the first and second lateralimages IMG1L, IMG2L. The first image IMG1 is overlaid as asemi-transparent image. In particular, the image processor 5 modifiesthe first image data such that the first image IMG1 is displayed as apartially transparent image which overlies a portion of each of thesecond image IMG2 and the first and second lateral images IMG1L, IMG2L.

The present invention has been described with reference to first andsecond side-mounted cameras C3, C4 mounted to the wing mirrors. It willbe appreciated that the first and second side-mounted cameras C3, C4 maybe incorporated into towing mirrors for mounting to the wing mirrors ofthe vehicle V. Alternatively, the first and second side-mounted camerasC3, C4 may be mounted in other locations on the vehicle, for example onleft and right sides of a rear bumper of the vehicle. Alternatively, thefirst and second rear-mounted cameras C3, C4 may be incorporated into alamp housing, for example a side indicator housing or a rear lamphousing.

In a further variant of the present invention, the first and secondside-mounted cameras C3, C4 may be mounted to the trailer T rather thanto the vehicle V. For example, the first and second side-mounted camerasC3, C4 may be mounted at the front of the trailer T in arearwards-facing orientation. It will be appreciated that the first andsecond lateral images IMG1L, IMG2L may be used by other vehicle systems,for example to facilitate manoeuvring and/or parking of the trailer T.

In a still further variant, the vehicle V can comprise first and secondrear-mounted cameras for generating first and second rear images. Thefirst and second rear-mounted cameras could, for example, be disposed ina rear quarter of the vehicle V. The first and second rear-mountedcameras may be mounted in the rear bumper of the vehicle V; within leftand right rear-light clusters; within left and right roof bars; or atthe outer ends of a roof spoiler. The first and second rear-mountedcameras have respective fields of view directed behind the vehicle V.The first and second rear images may be combined with the second imageIMG2 generated by the second camera C2 disposed at the rear of thetrailer T. In this arrangement, the fields of view of the first andsecond rear-mounted cameras may encompass at least a portion of thefront of the trailer T. The image processor 5 can be configured torender the portion of the first and second rear images corresponding tothe trailer T as a semi-transparent image which is overlaid onto thesecond image IMG2. The extent of the first rear image IMG1 which isoverlaid as a semi-transparent image could, for example, be determinedin dependence on a determined hitch angle θ of the trailer T.Alternatively, or in addition, the image processor 5 may implement anedge-locating algorithm or a shape-recognition algorithm to determinethe extent of the trailer T. It will be appreciated that the compositeimage may be formed in conjunction with the first image IMG1, or withoutthe first image IMG1. Thus, in certain arrangements, the first camera C1may be omitted.

A variant of the embodiment above in which the first and secondside-mounted cameras C3, C4 are used to generate first and secondlateral images IMG1L, IMG2L will now be described with references toFIGS. 8 and 9. Like references will be used for like components whendescribing this variant.

The image processor 5 is configured to generate a fourth composite imageIMG7 in dependence on a hitch angle θ and optionally also a pitch angleα of the trailer T. The hitch angle θ and the pitch angle α define theangular orientation of the trailer T relative to the vehicle V.Specifically, the hitch angle θ and the pitch angle α are defined withreference to a reference frame of the vehicle V. The hitch angle θdefines the angular offset between the first longitudinal axis X₁ andthe second longitudinal axis X₂ in a horizontal plane. The pitch angle αdefines the angular offset between the first longitudinal axis X₁ andthe second longitudinal axis X₂ in a vertical plane. In the presentembodiment, the hitch angle θ and the pitch angle α are determined bytracking a target 21 disposed on the front of the trailer T.Specifically, the image processor 5 analyses the first image IMG1 toidentify the target 21 and to determine its position and orientationrelative to the vehicle V. The hitch angle θ and the pitch angle α canthereby be determined using image processing techniques.

As shown in FIG. 8, the second camera C2 is mounted to the trailer T ina rear-facing orientation, typically at the rear of the trailer T. Thesecond image IMG2 encompasses a region behind the trailer T and isreferred to as a rear image. As shown in FIG. 9, the second image IMG2has a horizontal dimension DH and a vertical dimension DV. The secondimage IMG2 has a first horizontal centreline CLH1 and a first verticalcentreline CLV1. The first horizontal centreline CLH1 and the firstvertical centreline CLV1 are virtual reference lines which bisect thesecond image IMG2 horizontally and vertically. The second camera C2 isfixedly mounted to the trailer T and has a central focal axis CX2. Thesecond camera C2 is arranged such that the central focal axis CX2 isarranged substantially parallel to the second longitudinal axis X₂, butcorrections can be applied to the second image IMG2 to allow for anyangular offset and/or translational offset from said second longitudinalaxis X₂. A virtual origin ∘ is defined by the first horizontalcentreline CLH1 and the first vertical centreline CLV1. The virtualorigin ∘ is coincident with the central focal axis CX2 of the secondcamera C2.

It will be appreciated that the orientation of the central focal axisCX2 relative to the reference frame defined for the vehicle V varies independence on the hitch angle θ and the pitch angle α of the trailer T.Thus, the content of the second image IMG2 varies in dependence on theorientation of the trailer T. As a result, there can be a discrepancybetween the second image IMG2 and the first and second lateral imagesIMG1L, IMG2L (which are generated by the side-mounted third and fourthcameras C3, C4 mounted to the vehicle V). In order to compensate forthis discrepancy, the image processor 5 is configured to select asub-section P1 of the second image IMG2 for incorporation into thefourth composite image IMG7. The sub-section P1 is selected from withinthe second image IMG2 to compensate for changes in the hitch angle θ andthe pitch angle α. By compensating for these angular changes, the fourthcomposite image IMG7 formed by the image processor 5 can provide asubstantially continuous view of the image behind the vehicle V. Thesub-section P1 has a second horizontal centreline CLH2 and a secondvertical centreline CLV2. The second horizontal centreline CLH2 and thesecond vertical centreline CLV2 are virtual reference lines which bisectthe sub-section P1 horizontally and vertically. If a predefined sectionof the second image IMG2 was used to form the fourth composite imageIMG7, discontinuities would be introduced into the fourth compositeimage IMG7 as the hitch angle α and/or the pitch angle α changed. Due tothe overlaying technique described herein to display a portion of thefirst image IMG1 as a semi-transparent image, any such discontinuitiesmay potentially be obscured, which may result in the formation of one ormore blind spot in the resulting composite image.

The selection of the sub-section P1 will now be described in more detailwith reference to FIG. 9. In the present arrangement, the horizontaldimension DH and the vertical dimension DV of the sub-section P1 arefixed, i.e. the sub-section P1 has a predefined size. However, the imageprocessor 5 is configured to vary the position of the sub-section P1within the second image IMG2 in dependence on the hitch angle θ and thepitch angle α. The image processor 5 determines a negative equivalent ofthe hitch angle α and the pitch angle α (by multiplying by −1), therebychanging the sign of the respective angles. The image processor 5determines the location of the sub-section P1 within the second imageIMG2 in dependence on the determined negative of the hitch angle α andthe pitch angle α. Specifically, the image processor 5 modifies theoffset between the first and second horizontal centrelines CLH1, CLH2 independence on the determined negative of the hitch angle θ; and betweenthe first and second vertical centrelines CLV1, CLV2 in dependence onthe determined negative of the pitch angle α. A horizontal offset ΔHbetween the first vertical centreline CLV1 and the second verticalcentreline CLV2 is determined in direct proportion to the determinednegative of the hitch angle θ. Similarly, a vertical offset ΔV betweenthe first horizontal centreline CLH1 and the second vertical horizontalcentreline CLH2 is determined in direct proportion to the determinednegative of the pitch angle α. When the hitch angle θ is zero, the firstand second vertical centrelines CLV1, CLV2 are aligned. When the pitchangle α is zero, the first and second horizontal centrelines CLH1, CLH2are aligned. The extent of the horizontal and/or vertical translation ofthe sub-section P1 for a given angular change can be determined withreference to a virtual image plane. The virtual image plane can bedefined at a known position along the central focal axis CX2 of thesecond camera C2. The image processor 5 can then combine the selectedsub-section P1 with the first and second lateral images IMG1L, IMG2L.The first image IMG1 is overlaid as a semi-transparent image to form thefourth composite image IMG7. In certain embodiments, the fourthcomposite image IMG7 may be formed without overlaying the first imageIMG1.

To compensate for the angular change, the image processor 5 can alsoapply one or more image correction transform to the sub-section P1, forexample to de-skew the image or to correct a perspective shift. Theimage correction transform can also be dependent on the hitch angle θand/or the pitch angle α. An image correction transform may also beapplied to compensate for optical distortion within the third camera C3.

In the above variant, the transverse and vertical dimensions of thesub-section P1 are predefined. However, the image processor 5 may bemodified also to vary a horizontal dimension DH and/or a verticaldimension DV of the sub-section P1 in dependence on the hitch angle θand/or the pitch angle α. Specifically, the horizontal dimension DH maybe varied in direct proportion to the hitch angle θ; and/or the verticaldimension DV may be varied in direct proportion to the pitch angle α. Byvarying the dimensions of the sub-section P1, regions of the first andsecond lateral images IMG1L, IMG2L generated by the second and thirdcameras C2, C3 which might otherwise be obscured by the trailer T (forexample as the hitch angle θ increases) can be incorporated intosub-section P1. The changes in the horizontal dimension DH can besymmetrical about a first vertical reference line corresponding to thenegative equivalent of the hitch angle θ; and/or the changes in thevertical dimension DV can be symmetrical about a first horizontalreference line corresponding to the negative equivalent of the pitchangle α. Alternatively, the changes in the horizontal dimension DH canbe asymmetrical about the first vertical reference line corresponding tothe negative equivalent of the hitch angle θ; and/or the changes in thevertical dimension DV can be asymmetrical about the first horizontalreference line corresponding to the negative equivalent of the pitchangle α. It will be appreciated that the extent of the variations in thehorizontal dimension DH and/or the vertical dimension DV may varydepending on the trailer configuration, for example its externaldimensions and/or axle location.

A similar technique may be applied to modify the first image IMG1 priorto overlaying the first image IMG1. For example, the first image IMG1may be cropped in a transverse direction in dependence on the hitchangle θ.

A modification of the above embodiment may comprise changing thehorizontal dimension DH of the sub-section P1 about the first verticalcentre line CLV1; and/or changing the vertical dimension DV of thesub-section P1 about the first horizontal centre line CLH1. The changesin the horizontal dimension DH and/or the vertical dimension DV can besymmetrical. Alternatively, the changes can be implementedasymmetrically.

It will be appreciated that other techniques can be used to determinethe hitch angle θ, for example by directly measuring the angularorientation of a trailer hitch relative to a ball joint mounted to thevehicle. For example, the image processor 5 may be configured to selectsub-sections of the first and second lateral images IMG1L, IMG2L independence on the hitch angle θ of the trailer T.

1. A display system configured to generate a view of a region behind a vehicle towing a trailer, the display system comprising: a camera configured to output image data corresponding to an image; and an image processor configured to receive the image data, and wherein the image processor is configured to select a sub-section of the image in dependence on a determined orientation of the trailer.
 2. The display system of claim 1, wherein the determined orientation comprises a hitch angle relative to the vehicle and optionally a pitch angle of the trailer relative to the vehicle.
 3. The display system of claim 2, wherein the image processor is configured to select the sub-section of the image in dependence on a negative equivalent of the hitch angle.
 4. The display system of claim 3, wherein the image has a first vertical centerline and the sub-section has a second vertical centerline; wherein the image processor is configured to select the sub-section such that a horizontal offset between the first and second vertical centerlines is directly proportional to the negative equivalent of the hitch angle.
 5. The display system of claim 2, wherein the image processor is configured to select the sub-section of the image in dependence on a negative equivalent of a determined pitch angle of the trailer.
 6. The display system of claim 5, wherein the image has a first horizontal centerline and the sub-section has a second horizontal centerline; and wherein the image processor is configured to select the sub-section such that a vertical offset between the first and second horizontal centerlines is directly proportional to the negative equivalent of the pitch angle.
 7. The display system of claim 2, wherein the sub-section has a predefined horizontal dimension and/or a predefined vertical dimension.
 8. The display system of claim 2, wherein the sub-section has a horizontal dimension which is determined in dependence on the hitch angle, and/or a vertical dimension which is determined in dependence on the pitch angle.
 9. The display system of claim 8, wherein the horizontal dimension is varied symmetrically about a vertical centerline of the sub-section, and/or wherein the vertical dimension is varied symmetrically about a horizontal centerline of the sub-section.
 10. The display system of claim 2, further comprising: a further camera, wherein the further camera is a second camera configured to output second image data corresponding to a second image; and wherein the camera is a first camera configured to output first image data corresponding to a first image.
 11. The display system of claim 10, wherein the image processor is configured to select a sub-section of the second image and to combine the selected sub-section of the second image with the selected sub-section of the first image, and optionally at least a portion of the first image is overlaid as a semi-transparent image onto the selected sub-section of the second image.
 12. The display system of claim 11, wherein selecting the sub-section of the first image and selecting the sub-section of the second image are for alignment of the combined images.
 13. The display system of claim 1, further comprising: a third camera configured to output third image data corresponding to a third image; and a fourth camera configured to output fourth image data corresponding to a fourth image; wherein the image processor is configured to combine the selected sub-section of the image with the third and/or fourth images to form a composite image.
 14. A rig comprising a vehicle and a trailer, wherein the rig comprises the display system of claim
 1. 15. The rig of claim 14, wherein the camera is mounted in a rear-facing orientation to the vehicle.
 16. The rig of claim 14, further comprising: a further camera; wherein the further camera is a second camera configured to output second image data corresponding to a second image; wherein the camera is a first camera configured to output first image data corresponding to a first image; and wherein the second camera is mounted in a rear-facing orientation to the trailer.
 17. The rig of claim 14, further comprising: a third camera configured to output third image data corresponding to a third image; and a fourth camera configured to output fourth image data corresponding to a fourth image; wherein the image processor is configured to combine the selected sub-section of the image with at least one of the third and fourth images to form a composite image; wherein the third camera is a first lateral camera configured to output first lateral image data corresponding to a first lateral image; and wherein the fourth camera is a second lateral camera configured to output second lateral image data corresponding to a second lateral image.
 18. A method of generating a view of a region behind a trailer coupled to a vehicle, the method comprising: receiving image data corresponding to an image from a camera; and selecting a sub-section of the image in dependence on a determined orientation of the trailer.
 19. The method of claim 18, wherein the determined orientation comprises a hitch angle relative to the vehicle and optionally a pitch angle of the trailer relative to the vehicle
 20. The method of claim 18, wherein the camera is mounted in a rear-facing orientation to the vehicle. 